(NEXSTAR) – Nearly three years into the COVID-19 pandemic, we’ve learned a lot about the virus, and have developed vaccines and antiviral treatments that make the prospect of contracting the virus less deadly for most people. But one aspect of the virus that remains frustratingly mysterious, and scary to many, is the range of outcomes called “long COVID.”

Long COVID is a broad term describing complication that can last weeks, months or even years. Some people have shortness of breath, while others have damage to their senses of smell and taste. Some who suffer from long COVID experience debilitating fatigue and brain fog.

However, as time goes on, the chance of getting long COVID seems to be diminishing, new research suggests.

“The odds of having long COVID, we do see that rate is going down,” said Dr. Michael Gottlieb with Rush University Medical Center, who co-led a recent study on persistent COVID symptoms.

The study found people were more likely to suffer prolonged symptoms if they caught COVID in the “pre-delta period,” compared to the delta and omicron waves of 2021 and 2022. However, the difference has nothing to do with the variants. It has everything to do with vaccination and repeat infections.

“It is generally accepted that, on average, later infections with the same virus are going to be somewhat milder, and have somewhat less of a risk of causing long COVID symptoms,” agreed Dr. David Dowdy, an epidemiologist at Johns Hopkins Bloomberg School of Public Health.

Dowdy explained that on average – though there are exceptions – someone’s second or third COVID infection is less severe than their first. If you get over COVID in a few days while resting at home, you’re less likely to have issues that stick around for months. Whereas if you go to the ICU – with COVID-19 or any virus – you’re more likely to have a long road to recovery.

Repeat infection isn’t the only thing driving down the odds of catching long COVID. Vaccination plays a major role, research shows. People who get vaccinated, even if they experience a breakthrough infection, are less likely to have long COVID, according to the Centers for Disease Control and Prevention.

Gottlieb said his research also suggested vaccination reduces the risk of long COVID across variants.

“The odds are going down, but it’s not going down because of pure time. It’s going down because of things we’ve done,” said Gottlieb. “By getting vaccinated, it reduces that risk. And because more people have been vaccinated – or they have prior COVID, so they have some basic immunity in place – it reduces your longer term risk.”

Despite the odds trending in the right direction, many people are still suffering from a bout with COVID they had years ago. At least 65 million people globally are estimated to have suffered from long COVID, according to research published last month.

“There has definitely been a decrease in incidence of this complication over time, but because so many people have gotten COVID, there’s still a huge number of people suffering from prolonged symptoms,” said Dr. Paul Sax, the clinical director of infectious diseases at Brigham and Women’s Hospital who co-led the study with Gottlieb. “So there’s some good news and not-so-good news in that statistic.”